Control electrode for discharge tubes



Sept. 9, 1952 W. W. WATROUS, JR

CONTROL ELECTRODE FOR DISCHARGE TUBES Filed Jan. 5, 1951 IN V EN TOR. WMWWW w bill. IIIIIII Patented Sept. 9, 1952 CONTROL ELECTRODE FOR DISCHARGE TUBES Ward W. Watrous, Jr., Chatham, N. .l., assignor' Q to Chatham Electronics Corporation,v Newark, N. J a corporation of New J ersey- Application January 5, 1951, Serial No. 204,602

6 Claims. 1

This invention relates to control electrodes or grids used in heavy duty electron discharge tubes;

The structure of the control electrode is designed primarily to permit unequal heating of the electrode without buckling or changing the space relationship to other electrodes. 7

It has been customary to make control electrodes or grids of fine wires, woven mesh, or perforated plates, and in'the majority of vacuum or gaseous discharge devices, the problem of unequal heating is of little or no consequence. However, in certain types of high power tubes, Where the control electrode structure calls for large diameter, rugged, and thick pieces of metal, there is always the possibility that during exhaust or operation, the unequal heating may cause the structure to buckle, move out of alignment, either temporarily or permanently, and seriously affect the operation of the tube. This is especially true of tubes, such as hydrogen thyratrons, where the-control electrode is mounted in close proximity to the anode and where thereare numerous shields which enclose the grid and confine the heat'generated by the discharge.

One of the objects of this invention is to-provide an improved control electrode structure which avoids one or more of the disadvantages and limitations of prior art structures.

Another object of the invention is to limit the buckling of discharge tube electrodes when they are heated unequally by eddy currents during rangement which will protect the, control elec-v trode and eliminate short circuits to the anode and cathode.

The invention comprises a control electrode for discharge tubes which includes a disk or circular form with a solid periphery. Radial slots for the passage of electrons and ions are cut in the electrode and the central portion is cutout completely. A number of the radial slots are cut so as to intersect the central hole, thereby pro- .ducing triangular shaped components which have their base at the periphery and their apex near the center of the electrode. This design allows the outside of the structure to be heated to a very high temperature Without buckling the central portion. Conversely, the central portion may be raised to a very high temperature while the periphery is cold without changing the plane configuration of the electrode.

For a better understanding of the presentin vention, together with other and further objects thereof, reference is made to the 'iollowing' de.-'-

scription taken 'in connection with the 'acco mapanyingdrawings;

Fig. 1' isa crosssecti'onal View. of thecontrol electrode and an anode.

Fig. 2 is a plan view'of the control electrode structure taken along line 2-2 of Fig. 1.

Fig. 3 is a cross sectional view similar to Fig. 1, but showing how three control electrodes may-be mounted adjacent to a single anode.

Referring now to Fig; 1', an anode Ill issup-- ported by a rod-like support II which acts both as a lead-in and a support within a tube envelope (not shown). A control electrode I2 is mounted parallel to the anode It, and is supported by a flange l3 formed alongthe periphery which is welded or otherwise secured to-a shield structure M. A bafiie I5 is mounted under" the control electrode and is secured by'brackets' I6 which are attached to the control electrode.

The center of the bafil'e is formed in a step-like arrangement so that a retaining disk Il may be attached to the central portion thereof by welding or by a rivet l8, and when so attached,'the' upper surface of the disk lies in the same plane as the upper surface of the control electrode.

As will be seen in Fig. 2, the control electrode structure contains radial slots 20 and 2!, and at the center of the control electrode a circular-area is removed. The slots 20 are continuedtoward .the center so that they intersect the central area,

thereby forming triangular segmentsfi 'not connected to each other at the center. Slots 2|" are added for control purposes and do not meet the central cut out portion. It will be obvious that other slots or perforations may be cut inthe control electrode if additional control means are called for by the design and operation of the electronic device. The end portions of the triangular segments are bent in to form an offset so that their ends 23 (Fig. 1) may move freely in the space between one of the steps in the bailie l5 and the bottom surface of the disk l1. Space is provided so that considerable radialmovement of the ends is possible.

- which is not duplicated by the centralporti'on,

and the electrode is permanently stretched in a radial direction. Then, when the heat gradually moves to the center of the electrode, the central portion expands and buckles either towards the, anode or away from it, altering the characteri's-' v In the oper-- ation of this device it is frequently necessary tics of the tube and, in extreme cases, producing short circuits between the anode and the control electrode.

The present design permits the application of large amounts of high frequency power to the control electrode during the pumping process. Since the applied heat at the periphery does not stretch the central part of the electrode, the triangular segments merely pull away from the center of the tube without stretching, the points 23 moving in the annular slot between the disk I! and the baflle [5. When the electrode resumes an even over-all temperature or when it is cooled down to room temperature, the points of the triangular segments will again move in towards the center,.but without buckling and without changing the plane characteristic of the upper surface of the electrode. During the heating and cooling cycles, which are necessary in pumping the electron discharge tubes, electrodes often tend to buckle a slight amount due to inherent strains which were set up in the material during fabrication. The central support which the bafile' l5 supplies to the control electrode 12 tends to eliminate such movement by holding the central portions of the control electrode in a definite relation to the anode, thus providing an additional safeguard against out-of-alignment;

Fig. 3 is an alternate construction which indicates how three control electrodes may be mounted together. The anode Ill is mounted as usual in parallel arrangement to the first control electrode I2. is removed'in the same manner as shown in Figs. 1 and 2, and the washer l! consists of a metallic diskheld by a rivet or screw 25. The spacer 26 between the central points of electrode [2 and a second electrode 21 must necessarily be an insulator, and similar spacers 30 and 3|, which hold a third control electrode 32, must also be insulators. The central mounting arrangement, consisting of the top disk 25 and the three insulating spacers, may be conveniently mounted by a rod 33 which is attached to any convenient portion of the tube structure. The operation of this arrangement is essentially the same as the operation of the arrangement shown in Figs. 1 and 2 since any unequal heating which may occur during the pumping or operation of the tube will be taken up by I the annular slots between the disk and the central While there have been described and illustrated The central part of this electrode.

specific embodiments of the invention, it will be obvious that various changes and modifications may be made therein Without departing from the field of the invention which should be limited only by the scope of the appended claims.

What is claimed is:

1; A control electrode for electron discharge devices comprising, a fiat circular metallic plate having radial slots formed therein, a plurality of said 'slots extended to intersect one another at a central position thereby forming triangular sectors jointed to each other at the plate periphery, and a supporting structure at the central position for retaining the free ends of the sectors in the plane of the plate while permitting radial movement.

2. A control electrode for electron discharge de-- having radial slots formed therein, a plurality of said slots extended to intersect one another at a central position thereby forming triangular sectors jointed to each other at the plate periphery, and a supporting structure at the central position for retaining the free ends of the sectors in the plane of the plate while permitting radial movement, said supporting structure comprising a' central position thereby forming triangular sectors joined to each other at the plate periphery, and a supporting structure at the central position for retaining the free ends of the sectors in the plane of the plate while permittingv radial movement, said supporting structure comprising a cir-. cular member having an annular slot for slidably engaging the ends of the sectors.

4. A control electrode for electron discharge devices comprising, a fiat circular metallic plate having radial slots formed therein, a plurality of said slots extended to intersect one another at a central position thereby forming triangular sectors joined to each other at the plate periphery, a

supporting structure at the central position for.

retaining the free ends of the sectors in the plane of the plate while permitting radialmovement, said supporting structure comprising a circular member having an annular slot for slidably engaging the ends of the sectors, and a secondary supporting structure secured to the plate periphery for holding the circular member in place.

5. A control electrode for electron discharge devices comprising, a fiat circular metallic plate having radial slots formed therein, a plurality of said slots extended to intersect one another at a central position thereby forming triangular sectors joined to each other at the plate periphery, and a supporting structure at the central position for retaining the free ends of the sectors in the plane of the plate While permitting radial movement, the free ends of the sectors formed in an offset manner thereby permitting a continuous plane surface which includes the upper faces of the sectors and the supporting structure.

6 A control electrode for electron discharge'devices comprising, a flat circular metallic platehaving radial slots formed therein together with other openings, a plurality of said slots extended .,to intersect one another at the center of the electrode forming triangular sectors joined to 7 each other at the plate periphery where they are secured to a common mounting means, and a supporting structure at the central position for re taining thefree ends of sectors in the plane of the plate while permitting radial movement, the free ends of the sectors formed in an offset man-. ner thereby permitting a continuous plane surface which includes the upper faces of the sectors and the supporting structure.

WARD W. WATROUS, J R.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,201,731 Hull May 21, 1940 2,473,793 Gardner June 21, 1949 

